Ultra high frequency modulator



oct. 3, 1939. y w. R. KOCH `2,171.1.,701

I ULTRA HIGH FREQUENCY MODULATOR l Filed July 28, 1937 Ill-g Manz/mja@ y Inventor Patentedvoct. 3, 1939 UNITED STATES PATENT oFFlc'E ULTRA man FREQUENCY MonULA'ron Winfield R. Koch, Merchantville, N. .1., assignor to Radio Corporation of America, a corporation of Delaware Application July 28, 1937, Serial No. 156,054

6 Claims. '(Cl. 179-1715) My 'invention relates'to ultra high frequency modulators, and particularly to means for frequency modulating an ultra high frequency res-` onant line circuit.

It has been found that generatorsof currents of 50 megacycles per second and upwards may be better stabilized by resonant transmission lines than by piezo-electric crystal controls with their .attendant difficulties. In one aspect, my 'invention contemplates varying the characteristic of suchV stabilizing ultra high frequency resonant line .circuits to thereby frequency modlator by means of amplitude modulated currents of a lower frequency.

Another object is to provide means for varying the effective stabilizing frequency of a resonant line.

An additional object is to provide a stabilizing resonant line including magnetostrictive material and means for modulating the output of the line by modulations of said magnetostrictive material. A still further object of my invention is to provide means for modulating an ultra highfrequency carrier without the application of electrical power. q n

My invention may be best understood by reference to the accompanying drawing, in which Fhgure l is a schematic circuit diagram of a resonant line and means for modulating said line,

Figure 2 is a modification of Fig. l and illus,- trates one embodiment of my invention applied to a concentric resonant line,

Figure 3 is a circuit diagram showing a concentric line and a crystal modulator applied thereto,

Figure 4 is a circuit diagram illustrating a modified form of magnetostrictive modulator and concentric line,

Figure 5 is a schematic illustration of a concentric line which is modulated by sound waves,

and

Figure 6 is a schematic diagram of a circuit will be retained and the modulation characterwhich produces frequency modulated waves through the use of amplitude modulated waves. Referring to Fig. l, a pair of rmagnetostrictive members I, 3 form a resonant transmission line 5 which is connected to a thermionic oscillator l 1. 'Ihe oscillator may be of the Barkausen-Kurz, magnetron, or any suitable type of ultra. vhigh frequency current generator. The transmission line 5 is surrounded by a solenoid 9 which is ener- 4 gized by currents from a modulator Il. 10

If no modulation currents are impressed on the resonant line 5, the frequency of the o :i1- lator will be determined by the characteristics of the line, and in particular by its length. The line will stabilize the frequency oi.' the oscillator. When modulation currents are impressed on the solenoid, these currents will .exert forces on the magnetostrictive material of the members of the line, alter its length, and hence the resonant frequency of the line. Thus, the line both stabilizes the frequency and modulates the frequency of the currents generated bythe oscillator.

Referring to Fig. 2, a concentric resonant line I3 is made up of an outer member I5,.an inner member I1, and an armature member I9 mounted on'the top of the inner member. -The outer member I5 and the inner memberv I1 are made of magnetcstrictive material. A solenoid 2I,

surrounding the concentric line I3, is connected to a modulator 23. The line I3 is energizedby 30 anoscillator 25.

The'foregoing construction shortens the length of the line because of the increased capacity between the armature I9 and the end of the outer member I5. When the modulation'currents are passed through the solenoid 2|, they length of the magnetostrictive member ol? the concentric line will be Varied to thereby modulate the frequency of the currents stabilized bythe line I3. The undesirable effects of eddy cu'rrents in the outer member I5 may be avoided by oneor more slits in the outer member. The stabilizing effects of the line on the carrier 'currents of the oscillator istics described above added'thereto'.

In Fig. 3 the `modulation is effected, not by magnetostrictive forces, but by. piezoelectric effects. A concentric line 21, comprising an outer member y29 and ,an inner member 3l, is coupled to an oscillator 32. The inner member is made hollow to thereby accommodate a connecting wire. A lpiezo-electric member 33 is mounted on a conductor 35 or electrodewhich is insulated from the inner member by an insulated plate 31.

2 l f' V 2,174,701

l The conductor 35 is connected to a modulator 39 and a biasing battery 4|.

In the operation of the circuit of Fig. 3, the oscillator currents are stabilized by the concentric line to thereby maintain the carrier frequency substantially constant. When modulation potentials are applied to the piezo-electric crystal 33, the crystal will undergo changes in its thickness which will vary the capacity between the conductor 31 and the outer member 29. This vaation in capacity will, in effect, modulate they concentric line 21 and hence the frequency of the carrier currents.

In the circuit of Fig. 4, a concentric line 43 is used. 'I'he line consists of an outer member 45, an inner member 41, an armature 49 which is fastened to the inner member and a diaphragm 5| which is attached to the outer member 45. The diaphragm is made of bimetal; one of the metals is magnetostrictive. The dia.- phragm may be slotted to eliminate eddy current losses. A solenoid 53, energized by a modulator 55, actuates the magnetostrictive portion of the diaphragm.

Because one portion of the diaphragm is responsive to magnetostrictive forces, and the other is not, the diaphragm will bulge toward or away from the armature 49. The diaphragm movements will vary the capacity of the resonant concentric line and hence the period of carrier currents from the oscillator 51 which is coupled tions. The upper portion of the inner member 6| includes an armature 61. An acoustic diaphragm 69 ismounted on the end of the outer conductor 63 in spaced relation to the amature 61. Soun waves may' be impressed directly on the diaphragm 89. lThe diaphragm actuated by such waves will vary the capacity of the concentric line and hence its resonant frequency. The variation in capacity will frequency modulate the line 59 and the output from the oscillator 65. This arrangement is particularly adapted to an ultra high frequency portable, transmitter because of the absence of apparatus' and the power supply usually required for modulation. In installations where weight and power supplies are not important factors, the diaphragm 69 may be driven by a loudspeaker motor or the like.

A schematic circuit diagram of the application of the invention to an ultra high frequency transmitter and frequency modulator is shown in Fig. 6. In this circuit, Ia concentric line 1| is arranged with an outer member 13 and an inner member 15. A diaphragm 'l1 is mounted on the top of the outer conductor 13. An armature 19 is mounted on top of the inner member 15 and adjacent the diaphragm 11. An oscillator 8|, supplying ultra high frequency currents, is coupled to the concentric line 1|. A modulator 8,3 and an intermediate frequency oscillator are arranged to supply a solenoid 81 with amplitude modulated intermediate frequency currents which actuate the diaphragm 11 through the reaction between the magnetic eld set up by the currents in coil 81 and the eld due to the eddy currents in the diaphragm. The intermediate frequency is chosen so that the diaphragm will have too large an inertia to follow the individual intermediate frequency waves.

The diaphragm will, however, follow the average amplitude or modulation wave. Thus operated,

the carrier currents from the oscillator 8| are stabilized by the concentric line and modulated as described. The greater the current through coil 81, the greater will be the eddy current induced in the diaphragm, and the greater will be the depressing of the diaphragm, resulting in a greater decrease in frequency of oscillator 8|.

I have described several modications of my invention which" provide means for applying modulating signals to a resonant line which is used to stabilize an ultra high frequency oscillator. The resonant line serves the dual pufpose of modulation and stabilization, and permits an efficient application of wide range frequency modulation to an ultra high frequency carrier. In this type of modulation, the anode voltage on the oscillator may be continuous, thereby maintaining high grid impedance and low grid circuit power losses.

While I have specifically described the invention as applied to frequency modulation of the direct or double modulation type, it should be understood that my invention may be applied to vary the coupling between the oscillator and an antenna to modulate amplitude. It is also possible to apply the invention as shown to the automatic control of the frequency of the'heterosuch cases, changes in the intermediate frequency currents are applied to'the resonant line circuit to thereby change the frequency of the heterodyne oscillator to maintain constant intermediate frequency currents.

vI claim as my invention:

1. An ultra high frequency device including a line resonant to ultra high frequency currents. said line being made in part at least of a magnetostrictive material, and means for applying magnetostrictive forces to said material to thereby vary the physical proportions and thus the resonant characteristics of said line.

2. A resonant line for ultra high frequency oscillations, said line being made of magnetostrictive material, and means for applying magnetostrictive forces to said material.

3. A concentric line for ultra high frequency currents comprised of an inner member and an outer member, one of said members being-made of magnetostrictive material, and means for applying magnetostrictive forces to said one member.

4. In a device of the character of claim 3, an armature attached to said inner member for increasing the capacity of said line.

5. A device of the character of claim 3 in which said means for applying magnetostrictive forces includes a solenoid surrounding the element made of magnetostrictive material.

6. An ultra high frequency oscillator coupled to a concentric line including an inner member, outer member, a bimetallic diaphragm secured to said outer member, and an armature secured to said inner member; one of said bimetallic elements being responsive to magnetostrictive forces; and means for varying the length of said concentric 'line by applying magnetostrictive forces to said diaphragm, whereby said oscillator is modulated.

WINFIELD R. KOCH.

dyne oscillator of a superheterodyne receiver. In 

